This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have developed an in silico model that predicts varying levels for phenotypic robustness in populations evolving under constant and fluctuating environments. This project will test these predictions using yeast as a model system. Various yeasts will be evolved under constant or fluctuating environments. Samples will be taken over the course of the experimental evolutions and subjected to microscopy after staining and sequencing. Specifically, the high-throughput microscopic image analysis of individual yeast cells, stained for cell walls, actin, and nuclei, will serve to calculate phenotypic robustness values. We hypothesize that these values will differ during the course of evolution and between constant and fluctuating environments. We also hypothesize that robustness and fitness will be positively correlated.